The present invention is based on an air separator with the features of the air separators according to WO 93/09883 of the same applicant and also according to German Offenlegungsschrift No. DE-OS 24,26,295. The separator housing is helical in both cases and in the case of the present invention, the separator housing has a tangential separation air inlet, an inlet for the material to be separated parallel to the separation air inlet, as well as an axial fine material outlet. The fine material outlet is preceded by a separation wheel, through which the material to be separated is blown radially from the outside to the inside, and from which the separation air mixed with fine material is discharged axially, is removed from the separator housing through the separated material outlet and is fed to, e.g., a filter. After tangential entry into the separator housing, the material to be separated rotates around the axis of the separation wheel on a helical path, the coarse material enters the area of the helical flow located radially on the outside, it is separated from the mixture of separation air and fine material, and leaves the separator housing through a coarse material outlet.
In both cases, after tangentially entering the separator housing, the separation air first enters the flow channels of a blade ring with adjustable blades before mixing with the material to be separated takes place. While having the same design, the two blade rings are completely different due to the completely different tasks. In the case of the air separator according to DE-OS 24,26,295, the blade ring is the actual separation means, i.e., the separation of the particle containing gas flow, of the "material to be separated" into the fine material component, on the one hand, and into the coarse material component, on the other hand, takes place in the blade ring. Thus, the separation wheel is only an additional component. Based on the consideration that during of separation, the fine material can be contaminated with spray particles, which are formed after collision with other particles or after rebounding from the coarse material outlet, in the blade ring. The purpose of the separation wheel is to prevent these spray particles from entering the fine material outlet, and the separation wheel is therefore operated at a cut point which is above the coarsest cut point that can be set with the helical air separator, i.e., above the cut point that can be set with the stationary blade ring.
The conditions are fundamentally different in the air separator according to WO 93/09883. The separation takes place in the separation wheel in the air separator described there. While the separation into fine material and coarse material takes place in the stationary blade ring in the first air separator discussed above, the separation into fine material and coarse material takes place in the separation wheel, i.e., in the rotating blade ring, in the air separator according to WO 93/09883. While a rotating blade ring is an additional component, which has a special function in terms of catching spray particles, in the first air separator, the stationary blade ring is an additional component in the second air separator, and this blade ring has a special function, which consists of ensuring uniform conditions for the separation air over the entire circumference of the separation wheel. The blades of the stationary blade ring are therefore designed, arranged and adjustable such that due to the adjustment of the blades of the stationary blade ring in the annular space between the blade ring and the separation wheel, a helical air separation can be achieved. This provides a coarser separation size than would correspond to the conditions prevailing at the outer edges of the blades of the separation wheel. Consequently, spray particles are caught in one case, and the flow conditions at the outlet of the blade channels of the separation wheel are changed in the other case.
Regardless of this fundamental difference, the above-mentioned two air separators also differ by a different design of the coarse material discharge. In both cases, a separation air component is located radially on the outside and receives coarse material, which is peeled off with an edge. The coarse material is discharged with a screw arranged downstream of the edge in the case of the separator according to DE-OS 24,26,295. In contrast, the coarse material is peeled off by a properly arranged baffle plate in the case of the separator according to WO 93/09883. The baffle plate and especially the screw are additional components, which not only cause higher costs and additional weight, but are also subject to wear. In recognizing this circumstance, the basic task of the present invention is to design an air separator with the features according to the prior art discussed above but with neither a baffle plate nor a screw being necessary for discharging the coarse material.